When comparing exercism.io vs CodingBat Java, the Slant community recommends exercism.io for most people. In the question“What are the best online resources for learning Java?”exercism.io is ranked 1st while CodingBat Java is ranked 8th. The most important reason people chose exercism.io is:

Rather than merely test for code correctness, Exercism uses peer review to improve general programming techniques. Users are encouraged to comment on others' solutions, and refine their own based on feedback.

Pros

Pro

Human review and feedback

Rather than merely test for code correctness, Exercism uses peer review to improve general programming techniques. Users are encouraged to comment on others' solutions, and refine their own based on feedback.

Pro

Practice with production tools

Unlike many code practice websites, Exercism requires the user to develop and test entirely offline, submitting only the finished code. This promotes familiarity with essential tools and workflow, not just the bare language.

Pro

Singular focused excersises

Each exercise chapter focuses on a characteristics such as, arrays, strings, logic, recursion etc. This is useful as it does not overload the beginner nor the expert, as they get the chance to sharpen their skills.

Pro

Can be used to practice TDD (Test Driver Development)

By providing an array of tests that either pass or don't, the learner can focus on making each test pass in turn, until all become green.

Pro

Contains all necessary documentation to get started

There is a page with a basic explanation for each chapter.

Pro

Each submitted solution is checked against an array of tests

Pro

The text editor is basic and provides no context-assistance

By providing feedback only after compilation, the user has to pay attention to the language syntax from the beginning. This, in contrast to most modern IDEs, helps to build awareness and good habits.

Pro

Contains many basic problems, organized in various categories

The user can track their progress in solving a problem via Progress Graphs that show green tests and errors over time.

Cons

Con

Custom commandline client

Exercism requires using a CLI utility to fetch and submit exercises. This is inconvenient compared to web-only alternatives, and poses an additional barrier to entry for some users.

Con

It does not provide a Getting Started guide

Thus the learning curve could be steep for the complete beginner. Even though there is plenty documentation, it takes some initiative (and time) to study it and get started.